Re: Veritas ODM and Oracle 9i

rlro99_at_hotmail.com (Ralph) wrote in message news:<e2c49cae.0411300747.50aa4f3f_at_posting.google.com>...
> Oracle 9.2.0.4 (64-bit)
> Veritas version 1
> Solaris 9
>
>
> We have performed various tests on Oracle db_file_scattered_read
> performance in various combinations of:
>
> VxFS - with and without ODM
> VxVM partition - with and without ODM
> VTOC partition - with and without ODM
>
> and tried various combinations of db_block_size.
>
> Whilst we can get VxFS and any raw partition to perform IOs in
> db_file_multiblock_read_count * db_block_size requests, any use of ODM
> always results in the transfers being of db_block_size. This is
> clearly less effcient since more requests must be issued for this kind
> of read.
>
> This seems at odds with the documentation which claims that odm_io()
> will perform sequential reads/writes, direct read/writes, scattered
> reads, dbwr batch writes etc in the most efficient manner available.
>
> Is there any way that the behaviour of ODM can be influenced such that
> scattered reads are performed in db_file_multiblock_read_count *
> db_block_size requests?
>
>
> Cheers
>
> Ralph

Hi, Ralph,

I don't know the answer and I'm interested. But did you measure the overall performance of using and not using Veritas ODM when you run a batch job or a series of short transactions/queries? I'm reading www.oracle.com/technology/deploy/availability/pdf/nitin_ODM.pdf. They seem to be proud of simplifying I/O-related system calls (by saving the time to look up in the syscall dispatch table I think) and eliminating filesystem-related overheard (write locks, going through kernel page cache). In any case, overall performance comparison would be more appropriate than looking at whether it transfers only one db_block_size or not.

BTW, did you get that info by using ktrace, setting 10298 event or other means? Can you post somewhere all your benchmark results? Thanks.

Yong Huang Received on Wed Dec 01 2004 - 09:07:58 CST